Check out the trailer and synopsis below.
"VIXEN JOINS TEAM ARROW – Oliver (Stephen Amell) realizes he needs help battling Darhk (guest star Neal McDonough) so he calls in an old friend – Vixen (guest star Megalyn E.K.). Using her magical ability to summon animal powers, Vixen gets a lock on Darhk’s location and the team goes to war. Meanwhile, Thea (Willa Holland) has a heart-to-heart talk with Malcolm (John Barrowman). Gregory Smith directed the episode with story by Marc Guggenheim and teleplay by Keto Shimizu & Brian Ford Sullivan (#415)." - The CW